Extruded anode



Feb. 24, 1942.

BY ROLLI HG lNGOTS ARE MILLED HND CHIPPED I NGOT BOOQ HEATED AND FORGED2 BLOOMS REHEAT AND FORGE H EATEI? AND RGLLE'D AND ROLLED ,ovAL AuooesG. F. GEIGER EXTRUDED ANODE Filed June 25, 1940 3 Sheets-Sheet 1 avax-r-RusmN INGOT'S GO TO PRESS DIRETLY FROM THE MOULD HEATED- ANODESVARIOUS SHAPES INVENTOR. GEORGE FGE/GE/S G. F. GEIGER l=eb. 24, 1942.

EXTRUDED ANODE Filed June 25, 1940 :5 Sheets- Sheet 2 IN V EN TOR. IGEORGE F GE /6E/? ATTORNEY Y I Feb. 24,- 1942.

ca. FL GEIGER EXTRUDED ANQDE Fi led June 25, 1940 3 Sheets-Shee,t 3

. INVENTOR.

GEO/FGEEGE/GE/P a am ATTORNEY Patented Feb. 24, 1942 EXTRUDED ANODEGeorge Fellmuth Geiger, Radburn, N. J., assignor to The InternationalNickel Company, Inc.,

a New York, N. Y., a corporation of Delaware Application June 25. 1940,SerialNo. 342,228 In Canada May 29, 1940 2 Claims. (01. 148-2) Thepresent invention relates to extruded anodes, and, more particularly, toextruded nickel anodes. v

Since the inception of the nickel plating industry, the workersintimately connected therewith have constantly striven to improve theanodes employed. Efiorts have been made to imsame structuralcharacteristics as rolled nickel anodes, slightly less uniformdistribution of the provethe uniformity of corrosion and the upper limitof acceptable corrosion. In addition, efforts have been made to controlthe amount of sludge produced and the amount of loose nickel producedduring corrosion by control of the com.- position of the anodes. Amongthe satisfactory solutions to these various problems has been the rollednickel anodes now available to the art. These rolled anodes, from atechnical viewpoint are highly satisfactory from the standpoint ofactivity, the upper limit of acceptable corrosion, the amount of loosenickel and the amount of sludge produced during corrosion. From amanufacturing standpoint the multiplicity of opera- .tions required toreduce the cast ingot to an anode of suitable size is a drawback. Thiswill be readily appreciated when the process of producing rolled anodesis reviewed. As those skilled in the art well know. the metal for ananode is first cast as an ingot. The ingots are then milled and chipped.The chipped ingots are then heated and forged to provide two blooms. Attimes however, a reheat is necessary. The blooms are again heated androlled and the operations repeated as often as is necessary to obtainthe required reduction in cross section to provide an anodeof suitabledimensions. It has been dis.- covered that anodes comparing favorably inevery respect 'from a chemical and an electrochemical standpoint can beproduced by a very much simpler process than the prior art rollingprocess.

It is an object of the present invention to produce anodes having thevaluable characteristics of roll 6. anodes by a simplified process.

It is a other object of' the present invention to producecarbon-containing and carbon-free nickel anodes having the desirablecharacteristics of rolled nickel anodes.

It is a further object of the present invention to provide nickel anodeshaving improved surface characteristics, good corrosion, and higheniciency.

It is likewise within the purview of the present invention to provideoxygen-free anodes havin the desirable characteristics of rolled nickelanodes. I

The present invention also contemplates the nickel oxide and slightlyless uniformity of grain size.

It is also within the contemplation of the present invention to providenickel anodes having the valuable characteristics of rolled nickelanodes from cast and/or forged billets.

Other objects and advantages will become ap parent from the followingdescription in which:

Fig. 1 is a diagrammatic flow sheet in asomewhat pictorial manner of theprior art process of producing rolled anodes;

Fig. 2 is a diagrammatic flow sheet clearly illustrating in a pictorialmanner the simplicity of the process of the present invention ascompared with the conventional process for producing rolled anodes;

Fig. 3 is a photomicrograph of transverse edge of a hot rolled nickelanode;

Fig. 4 is a photomicrograph of a transverse edge of an extruded nickelanode;

Fig. 5 is a photomicrograph of a longitudinal edge of a hot rollednickel anode;

Fig. 6 is a' photomicrograph of a longitudinal edge of an extrudednickel anode;

Fig. 7 is a photomicrograph of a transverse center of a rolled nickelanode;

Fig. 8 is a photomicrograph .of a transverse center of an extrudednickel anode;

Fig. 9 is a photomicrograph of a longitudinal center ofa rolled nickelanode; and

Fig. 10 is a photomicrographof a longitudinal center of an extrudednickel anode.

Generally speaking, the simplified process for producing the anodes,and, more particularly, nickel anodes having the valuablecharacteristics of hot rolled nickel anodes involves the fusion of amelt having a suitable composition which is cast preferably in ingotssomewhat smaller than those heretofore employed in the hot rollingproduction of nickel anodes. The casting is then introduced into anextrusion press of suitable size and having a die of suitable contourand the anodes extruded directly from the press.

The advantages in simplification of the manufacturing process forproducing nickel anodes having the valuable characteristics of nickelanodes will become manifest from a study of the flow sheet depicted inFig. l. As will be readily appreciated by those skilled in the art thereare a minimum of 9 or 10 steps in the process of producing rolled nickelanodes. These steps include millin chipping and heating the ingotfollowed shapes.

by forging the blooms. The blooms are then heated again, rolled, say ona 24 inch mill, reheated and rolled again, for example, on a 14 inchmill. These latter rolling operations are repeated as often as necessaryto produce anodes having the required dimensions.

A further drawback of the rolling process is the inflexibility of theprocess with respect to the shape of the anode produced. The hot rollingprocess as practiced by the industry at the present time produces butone shape anode, to wit: the so-called "oval anode, without a changefrom one pass to another or a roll change. Such a roll change is muchmore expensive than a die change as required in the extrusion process ofthe present invention. On the other hand in direct contrast to thisdisadvantage of the hot rolling process, the process of the presentinvention is very flexible as is well understood by those skilled in theart. The die by which the form of the extruded anode is controlled maybe designed to produce anodes of various and diverse Thus rounds, flatsand in addition various other shapes such as prismatic, half-round,half-oval and many other unusual shapes may be produced in oneoperation. As the hot rolling process is carried out at the present timeanodes cannot be produced in the latter unusual shapes withoutconsiderable expense. In addition to these manufacturing advantages theimproved extruded anode provides a certain other advantage. Thus theover-hauling of the ingot prior to hot rolling is eliminated sincepractically all of the outer skin of the ingot is left in the extrusionpress. Furthermore the surface of the anode is devoid of certain defectswhich are common in hot rolled nickel anodes.

The novel anode described herein possesses certain advantages over theconventional cast anodes of the prior art processes. For example, theextruded anodes of the present invention come from the press in asurface condition which is a considerable improvement over that of castanodes. The surface of the extruded anodes is smoother and free frommold pulls. Furthermore the extruded anode is free from slag inclusions,has a more homogeneous structure and a more uniform composition than thecast anodes now available to industry. From the foregoing it will bereadilyappreciated that the process of the present invention representsa long stride forward in the technical progress of electroplatmg.

In order thatthose skilled in the art may have a better understanding ofthe principles of the present invention the following discussion of themetallurgical, electrochemical and plating characteristics of the newextruded anode made from oxidized nickel will be given together with abrief discussion of similar characteristics of hot rolled nickel anodesas well as the cast anodes available to the industry at the presenttime.

The drawings, Figs. 3 to 10, provide means for differentiating betweenthe crystal structure of the new extruded anode and the prior art hotrolled anode. For comparison of the crystal structure of the prior artanode and the new ex- .truded anode, sections of the transverse edge,

the longitudinal edge, the transverse center and the longitudinal centerof representative anodes were taken and polished and etched in the usualmanner. The crystal structure of the transverse edge of a hot rollednickel anode is depicted at an enlargement of about 100 magnificationsin Fig. 3. As those skilled in the art will readily appreciate, thegrain size is uniform and relatively large. Furthermore, as is clearlyshown in .Fig. 3, the distribution of oxides and similar conand that thedistribution of oxide formations likewise is not as uniform as in thehot rolled anode. The uniform distribution of grain size and oxideformation characteristic of. hot rolled nickel anodes is readilyappreciated by an inspection of Fig. 5 However, in striking contrast tothe homogeneity of the hot rolled nickel anode, the banded structure ofthe extruded anode is manifest in the photomicrograph Fig. 6, as will beclearly seen. This is a photomicropragh of a section taken from alongitudinal edge of an extruded nickel anode. The distribution of grainsize is not uniform and the striations of oxides are manifest. Furtherevidence of these differences between the crystalline structure ,of theprior art hot rolled nickel anodes and the novel extruded anode may bereadily appreciated by those skilled in the art, from an inspection ofFigs. 7, 8, 9 and 10.

In view of the non-uniformity of distribution of oxides and thenon-uniformity of grain size it is surprising that uniform corrosion andproduction of only small amounts of loose nickel and sludge arecharacteristic of the new extruded anode. Those skilled in the art willappreciate the importance of this discovery when it is borne in mindthat the experts have taught that uniformity of distribution of theoxide inclusions is necessary to smooth corrosion and similar desirablecharacteristics of nickel anodes.

It has been found that after de-skinning the new extruded nickel anodethe degree of activity of the anode is practically the same as that of asimilarly de-skinned hot rolled nickel anode. As those skilled in theart know, it is customary to subject nickel anodes to a de-skinningprocess in which about 3% by weight of the anode is removed in apreliminary electrolytic treatment.

The new extruded nickel anode possesses several advantages as comparedwith the cast anode of similar or comparable composition. The surface ofthe extruded anode is smoother than that of a cast anode. Furthermore,the freedom from slag inclusions which is characteristic of the extrudedanode is an item which the practical elec troplater will appreciate. Itis manifest that such slag inclusions lower the content of availableanodic material, may well be the cause of uneven corrosion and are thesource of other drawbacks well known to those skilled in the art. Forexample, in cast nickel anodes there usually is present an increasedamount of loose nickel in the regions of slag inclusions. As is wellknown to those skilled in the art cast anodes frequently are marred bymold-pulls. The disadvantages of these inherent defects of a caststructure are too readily appreciated by those skilled in the art torequire lengthy discussion at this time.

Although lacking the homogeneity of rolled anodes, the new extrudedanode has a more unianodes will be appreciated by those skilled in theart.

Carbon- Carbon- Oxygenfree bearing free Electro 99. 76 99. 70 90. 9) 0.10 None None None 0. 25 None Trace 0. 005 0. 008 0. 003 Trace 0. 01 0.24 0. 14 Trace 0.04 0.04 0.04 01 to 0.03

Trace 0. 001 Trace 0. 0.05 0.09 0 01 to 0. 04

The value for nickel includes incidental amounts of cobalt usuallypresent in commercial nickel.

The ingot is cast in the usual manner and transferred directly to thecylinder of an extrusion press of suitable dimensions. The press isprovided with'a die having the desired contour which may be that of asquare, a circle, a rectangle, a semi-circle, a triangle, or ahalf-oval. In addition, anodes may be extruded having an irregular crosssection. It is preferred to maintain a temperature of about 900 to about1200 C. during the extrusion of the anode. The pressure required forextrusion depends upon the size and shape of the anode being extruded.Oval anodes having a major axis about 2 inches in length as comparedwith the major axis of 3% inches com? mon for rolled nickel anodes havebeen produced. As the extruded metal comes from the press it is quenchedin a 2% alcohol-water bath. From the foregoing description of the novelprocess it will be readily seen that a major por tion of the operationsnecessary to the production of good or satisfactory rolled anodes iseliminated. Those skilled in the art will readily appreciate theeconomic advantages arising from the elimination of these steps in theproduction of rolled nickel anodes.

Etched and polished edge sections of extruded anodes indicate that theaverage grain diameter at the edge is about 0001330001 inch, whereas theaverage grain size of; rolled nickel anodes at the edges is about 00021.The average grain diameter, as indicated by sections taken from thecenter of extruded anodes, indicates that at this point in the extrudedanode the grain size likewise is appreciably less than that of thegrains or crystals which are present in the center of rolled nickelanodes. Thus, the average grain size at the center for extruded anodes,is about 0.0016, whereas the average grain size at the center forrolled. anodes is about 0.0021. From the above values, it will be seenthat the average grain size throughout the rolled nickel anodes is thesame, whether the section be taken from an edge or from the center. Onthe other hand, the foregoing values clearly show that the grains orcrystals in the edges of the extruded anodes are somewhat smaller thanthe crystals in the center of the anode. In addition, the average grainsize for the entire extruded anode is about 67% of the average grainsize for the entire rolled anode.

-Although the present invention has been described in conjunction with aparticular embodiment thereof, those skilled in the art will readilyunderstand that variations and modifications are to be considered withinthe purview .of the specification and the scope of the appended claims.

I claim:

1. As a new article of manufacture, a hotextruded nickel electroplatinganode having a banded structure along the transverse axis of saidextruded nickel electroplating anode, said banded structure comprisingalternate areas of nickel substantially free from inclusions and areashaving relatively high concentration of inclusions, said bands beingdisposed in planes extendingin the longitudinal direction of said nickelelectroplating anode.

2. A process for producing extruded nickel electroplating anodes, whichcomprises establishing a bath of molten metal having a compositionproviding an acceptable nickel anode, casting at least a portion of saidmetal in a mold to form an ingot of slightly smaller size thanconventional ingots provided for subsequent reduction to blooms andbillets for rolling to electroplating anodes, and subjecting said ingotto suitable pressure in an extrusion press at temperatures of about 900C. and about 1200 C. to extrude a nickel electroplating anodesubstantially free from slag inclusion common to cast anodes, saidextruded nickel electroplating anode having areas of mutually differentgrain size, the grains of said anode being largest in the region of thetransverse center and smallest in the region of the surface of saidanode, said extruded nickel electroplating anode having a smoothercorrosion than cast nickel anodes and, in contrast to the non-uniformstructure of said extruded nickel electroplating anode, corrodingsubstantially as uniformly as rolled nickel electroplating anodes ofuniform structure, and producing substantially no more loose nickel andsubstantially no more sludge than rolled nickel electroplating anodes ofuniform structure and substantially the same analysis.

GEORGE FELLMUIH GEIGER.

